The goal of this project is to identify small molecules that treat amyotrophic lateral sclerosis (ALS), a uniformly lethal, unbeatable neurodegenerative motor neurons disorder. As an orphan disease, ALS has not generally been a research target for the pharmaceutical industry. We therefore believe it is incumbent on academic laboratories to undertake drug discovery programs for molecules that slow or reverse motor neuron pathology in ALS. This proposal endeavors to do this through four projects. Each is based on an existing in vitro cell model that recapitulates key pathobiological features of ALS. These models screen for compounds that (1) inhibit cell death induced by mutant superoxide dismutase (mSOD1);(2) down-regulate expression of mSOD1;(3) enhance glutamate transport by the major astroglial glutamate transporter EAAT2;and (4) accelerate degradation of mS01 protein. Each cell-based model is fully operational in high throughput screens that represent the initial step of our working strategy. The four projects are divided into two sequential phases as follows: Early phase: Aim 1 Perform high throughput screens (HTS) using a library (MIND library) of 38,500 compounds;Aim 2 Perform secondary, low throughput screening (LTS) assays to validate HTS hits and perform in vitro toxicology and dose response studies;Aim 3 Optimize the chemical structure of positive compounds using structure activity studies and/or medicinal chemistry. Late phase: Aim 4 Evaluate the lead compounds for pharmacokinetic (permeation of the blood brain barrier) and safety properties;and Aim 5 Determine the efficacy of the lead compound(s) in ameliorating motor neuron degeneration in a transgenic mouse model of ALS. In our view, this project is highly relevant to the mission of the NINDS. Small molecules therapies for motor neuron degeneration are likely to be beneficial not only in ALS but also in other neurodegenerative disorders and potentially in conditions such as stroke or traumatic brain and spinal cord injury. Lay Summary: This is a proposal to discover drugs to treat Lou Gehrig's disease, a lethal disorder that is largely ignored by most drug companies;drugs identified in this program may help other brain diseases.